Objectives: Pertussis vaccines containing a whole-cell pertussis component have effectively controlled pertussis disease in the US. Progress in the development and licensing of less reactogenic acellular pertussis vaccines was hindered by the lack of a laboratory correlate of clinical protection and of standardized assays for measurement of immune responses. To address this need, the Laboratory has undertaken the following projects: a) To work toward the international standardization of immunoassays used to evaluate the antigen and isotype specific responses to B. pertussis. b) to employ these assays to evaluate the serologic response in individuals immunized with pertussis vaccine. c) To develop new assays and animal models with the goal of defining a laboratory correlate of clinical protection. FY97 activities: 1. Published results of an international collaborative study to evaluate immunoassays used in acellular pertussis vaccine efficacy and immunogenicity studies. Analysis of the data set from the collaborative study has continued; the goal is to determine which statistical models most accurately describe the and define ELISA assay variability. 2. Completed analysis of immunoassay results on a sub-group of individuals (n=1200) from an NIAID-sponsored study who received one of the 12 differenc acellular vaccines as a fourth dose; a publication has been accepted for publication.3. INitiated analysis of a sub-gourp of individuals (n=350) from an NIAID follow-up study who received one of 6 different acellular vaccines as a fifth dose. The Section did not perform the primary serologic assays, but is performing approximately 600 assays on subsets of samples for qulaity control purposes and took a lead role in the analysis, presentation, and publicatino of the serologic data. 4. Continued evaluation of a mouse leukocytosis model which is able to detect pertussis toxin (PT)-neutralizing antibodies in human serum, and to corrlated these results with PT-neutralization activity as measured in a tissue culture assay and PT-binding activity as measured by ELISA.5. Assisted Dutch public health officials in evalutaion of serologic assays used in their investigation of a recent pertussis outbreak.